Field of the Disclosure
This present disclosure is directed to drilling wellbores in the earth, to systems for pumping drilling fluid (“mud”) for such operations, to mud pumping systems and valves for them, and to a valve that has opposed curved sealing surfaces on a valve member and on a valve seat to thereby facilitate effective sealing, and methods of their use.
Description of Related Art
The prior art discloses a wide variety of drilling systems, apparatuses, and methods including, but not limited to, the disclosures in U.S. Pat. Nos. 6,944,547; 6,918,453; 6,802,378; 6,050,348; 5,465,799; 4,995,465; 4,854,397; and 3,658,138, all incorporated fully herein for all purposes. The prior art discloses a wide variety of drilling fluid pumps (“mud pumps”) used in drilling operations and pump systems, for example, and not by way of limitation, those pumps and systems disclosed in U.S. Pat. Nos. 6,257,354; 4,295,366; 4,527,959; 5,616,009; 4,242,057; 4,676,724; 5,823,093; 5,960,700; 5,059,101; 5,253,987; in U.S. applications Ser. No. 10/833,921 filed Apr. 28, 2004(all said U.S. references incorporated fully herein for all purposes).
A drill bit carried at an end of a drillstring is rotated to form wellbores in the earth. Certain drillstrings include tubulars which may be drill pipe made of jointed sections or a continuous coiled tubing and a drilling assembly that has a drill bit at its bottom end. The drilling assembly is attached to the bottom end of the tubing or drillstring. In certain systems, to drill a wellbore, the drill bit is rotated (e.g., by a top drive, a power swivel, a rotary table system, or by a downhole mud motor carried by the drilling assembly). Drilling fluid, also referred to as “mud,” is pumped through the wellbore under pressure from a pit or container at the surface by a pumping system at the surface.
In certain known mud pump systems, suction and discharge modules have valves therein that selectively control fluid flow through the module in an intake (suction) mode in which piston apparatus creates a vacuum drawing drilling fluid into the module and in an output mode (Discharge) in which the piston apparatus creates pressure forcing drilling fluid out of the module. In the suction mode, a suction valve opens allowing drilling fluid into the module while a discharge valve remains closed. In the discharge mode, the pressure of the drilling fluid closes the suction valve and opens the discharge valve.
Both valves, the suction valve and the discharge valve, are subjected to the erosive and damaging effects of the flow of drilling fluid. The drilling fluid contains drilled cuttings and debris which can erode valve parts (e.g. seats, stems, valve members, seals, guide bushings, insert, liners, wear plates etc.). Also, mud pumps which can pump relatively hot drilling fluid at, e.g., 500 to 2000 gallons per minute, force the erosive drilling fluid against the valve parts at high velocities which add to the fluid's damaging effects.
In many valves used in mud pump systems, a guide in the valve which is disposed across a flow path or guide fingers extending from a valve member into a valve seat guide a valve member so that valve member seats correctly and effectively against the valve seat. In many valves, the valve seat surface against which the valve member (or poppet) seats is, ideally, flat; and the surface of the valve member which sealingly abuts the flat seat surface of the valve seat is, correspondingly, and ideally, flat. A guide or guide fingers facilitate correct seating of the valve member's flat seating surface against the valve seat's flat seat surface. If either surface is not flat, or if one surface does not contact the other in a substantially parallel (flat surface to flat surface) manner, ineffective or inefficient valve operation may result.
The erosive and/or damaging effects of drilling fluid flow through a valve can damage the seating surfaces so that the ideal flat-surface-to-flat surface seating is not achieved. Also, the drilling fluid can damage a guide (e.g. ribs and a channel for receiving a stem or rod projecting from a valve member) or guide fingers so that the ideal surface seating is not achieved. In some instances, damage to a guide or to guide fingers results in a flat valve member surface contacting a flat seating surface at an angle so that effective valve closure is not possible or so that the valve is insufficiently closed for efficient operation. In some aspects, erosive drilling fluid flow renders initially-flat seating surfaces non-flat with resulting ineffective sealing and valve closure.
For these reasons in many mud pump systems, suction and discharge valves are repaired or replaced on a regular basis.
In many known mud pump valves, the valves are opened and closed by mechanically creating a vacuum or fluid pressure increase in the valve that overcomes a spring to allow a valve member to move. The movement of the valve member is not controlled, i.e., it is subject to a surge of fluid under pressure. As fluid pressure builds up to move a valve member, a corresponding amount of fluid builds up adjacent the valve. When the pressure is high enough, a relatively large charge of fluid goes through the valve at high velocity. This surge of fluid can have deleterious effects on valve parts, for example, such as the banging of the sealing surfaces together as a result of fluid rushing in because of a delay in the timing of the opening of the valve.
The present disclosure is directed to various methods and devices that may avoid, or at least reduce, the effects of one or more of the problems identified above.